Indian policy makers are looking for ways to tamp down American tech behemoths, a shift that could crimp growth potential in one of the biggest remaining open markets for their expansion.

India wants to slap new rules on Amazon.com Inc., Apple Inc., Alphabet Inc.’s Google, Facebook Inc. and other firms, using a page from China’s playbook to take control of its citizens’ data and shelter homegrown startups.

The proposed rules, which have emerged in recent weeks in a series of private, draft government policies, have U.S. tech companies concerned, according to familiar with the matter. American firms are betting billions on the Indian market because, unlike China’s, it has been relatively open to foreign competitors. That might be about to change.

“It is unprecedented and it needs to be taken very seriously,” said Vinay Kesari, a Bangalore-based technology lawyer specializing in regulatory matters who has worked with U.S. tech firms. “It could have huge implications.”